Unable to pull SPI MISO line down via device tree configuration

RE: Unable to pull SPI MISO line down via device tree configuration

Vidar Berg — Thu, 15 Aug 2024 10:07:36 GMT

Hi Alex,

I'm glad to hear that it worked, thanks for the update. Forgot to add earlier that there is a Kconfig setting (https://github.com/nrfconnect/sdk-zephyr/blob/98a344fe21a4439b0cd1d340635a6ccb3e166f46/drivers/flash/Kconfig.nor#L34) to make the driver automatically issue the power down (0xB9) command between SPI transactions, in case you had not seen it already.

Vidar

RE: Unable to pull SPI MISO line down via device tree configuration

Alex_S@Aperia — Wed, 14 Aug 2024 21:35:07 GMT

Hi Vidar,
That did the trick, sleep current dropped to where we want it to be.
Thank you so much,
Alex

RE: Unable to pull SPI MISO line down via device tree configuration

Vidar Berg — Wed, 14 Aug 2024 14:45:11 GMT

Hi, no problem. The 'low-power-enable' property is used when you want to configure the pins to their reset state (input, disconnect) after suspending the SPI peripheral. However, it cannot be used while the peripheral is enabled. Therefore, you should remove 'low-power-enable' for spi2_default. Everything looks correct apart from that.

RE: Unable to pull SPI MISO line down via device tree configuration

Alex_S@Aperia — Wed, 14 Aug 2024 14:02:29 GMT

Hi Vidar !
Appreciate prompt response.
So, given the fact that my flash is NOR and I need MISO pulled down, my pinctrl.dtsi should look like this ?

spi2_default: spi2_default {
    group1 {
        psels = <NRF_PSEL(SPIM_SCK, 1, 1)>,
        <NRF_PSEL(SPIM_MOSI, 1, 2)>;
        low-power-enable;
    };
    group2 {
        psels = <NRF_PSEL(SPIM_MISO, 0, 11)>;
        low-power-enable;
        bias-pull-down;
    };
};

RE: Unable to pull SPI MISO line down via device tree configuration

Vidar Berg — Wed, 14 Aug 2024 08:26:31 GMT

Hello,

Since SDK v2.0.0, the pull configuration has to be applied to the pinctrl node. I'm not sure why the miso-pull-down property was still present in SDK v2.1.2, but it has since been removed. In any case, the additional current consumption may be caused by leakage due to the MISO input becomes floating when the SPI flash enters the power-down state.

Here is an example on how you can enable pull-up on MISO with the 'bias-pull-up' property in your devicetree:

	spi2_default: spi2_default {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 1, 1)>,
				<NRF_PSEL(SPIM_MISO, 1, 2)>;
		};

		group2 {
			psels = <NRF_PSEL(SPIM_MOSI, 0, 11)>;
			bias-pull-up;
		};
	};

	spi2_sleep: spi2_sleep {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 0, 19)>,
				<NRF_PSEL(SPIM_MOSI, 0, 20)>,
				<NRF_PSEL(SPIM_MISO, 0, 21)>;
			low-power-enable;
		};
	};

Note: the SPI nor driver does not implement PM device power states or change the pin configuration. This means that only the "spi2_default" configuration will be used.

Best regards,

Vidar